Is there significant variation in the risk of gastric cancer associated with Helicobacter pylori infection

SUMMARY Helicobacter pylori infection is a risk factor for gastriccancer and most epidemiological studies have estimateda relative risk associated with infection in the order oftwo to four-fold. There is interest in the extent to whichthis risk estimate might vary between differentpopulations especially as several populations have beenidentified with low rates of gastric cancer despite a highinfection prevalence. Methodological differencesbetween studies make it difficult to compare the resultsof retrospective case-control studies to quantify thevariation in risk, but prospective studies indicate thatthere may be a six-fold variation in risk betweendifferent populations. It is likely that genetic and/orenvironmental co-factors are important in modifyingthe risk associated with H. pylori infection but there arefew studies that have fully investigated the role of suchco-factors. 3 Correspondence to: Professor D. Forman, Centre for Cancer Research,University of Leeds, Cookridge Hospital, Leeds LS16 6QB, UK.